Check valves typically employ a biasing mechanism such as a spring in combination with a plate or ball to ensure closure in the event of a reverse pressure condition. Other designs employ a diaphragm to open or close a channel in response to a pressure differential (see, e.g. U.S. Pat. No. 4,846,215 Barree).
Check valves that employ diaphragms as closure elements are typically constructed from at least three elements, with the diaphragm being sandwiched between two housing members (see, e.g. U.S. Pat. Nos. 3,633,605 Smith and 3,270,771 Morgan et al).
This invention provides a process for manufacturing a check valve at low cost from just two elements, and a check valve design which is particularly suitable for low-pressure-differential applications in which both low opening pressure and low leakage are desired.